When an antenna is designed on a wireless terminal (for example, a data card), the following technical problems exist, including the following. An available space of an antenna area is small; a target bandwidth is broad; and requirements are strict for a short distance test of a Specific Absorption Rate (SAR) value.
The SAR represents an amount of radiation that is allowed to be absorbed by an organism (including a human body) per kilogram, and is a most direct test value denoting an impact of the radiation on the human body. The lower the SAR value is, the smaller the amount of the absorbed radiation is. In a current SAR test specification, when an SAR value is required to be tested, a distance from each face of the data card to a human body torso model for an SAR test should not exceed 5 mm, and the SAR value should not exceed 1.2 mw/1 g. Therefore, it is a problem to be urgently solved to effectively reduce the SAR value without affecting other wireless performance indexes. Meanwhile, wireless communication has more and more requirements on a working bandwidth of the antenna, and it is hoped that an antenna may have multiple operational frequency bands on an ultra-wideband at the same time.
Currently, when the antenna is designed on the data card, built-in antennas in a form of monopole, Inverted-F Antenna (IFA), and Planar Inverted-F Antenna (PIFA) are widely used. The antennas of these forms are generally located at one end of the data card, and a data card single board acts as a “ground” of the antenna, which together constitute a radiator. During the implementation of the present invention, the inventor finds that: in the antenna design in the prior art, in one aspect, the near-field energy of the antenna radiation is concentrated, causing that the SAR value is relatively large; and in another aspect, the antenna bandwidth is limited, which cannot satisfy a growing bandwidth requirement.